This invention relates to a volume rendering method which projects an image provided by three-dimensional volumetric data on a two-dimensional plane. Volume rendering is an important technique for visualizing and analyzing three-dimensional data. It is widely used in for instance medical applications for visualizing data that have been obtained by for instance MRI and CT methods. For the visualization to be effective, it is essential to be able to perform the volume rendering in interactive rates. The rendering methods are usually performed by a processor such as a dedicated Graphical Processing Unit (GPU). For most common hardware-accelerated volume rendering techniques the data has to be stored in graphics memory as a 3D texture. Unfortunately there is no efficient way to update volumetric data on the GPU as needed for GPU-based algorithms. Although the new OpenGL frame buffer object extension allows rendering to slices of a volume, the current drivers do not provide an efficient implementation. The rendering methods have to be performed within the constraints (such as execution speed of instructions) of the GPU. Accordingly, efficient implementation of volume rendering techniques on the Graphical Processing Unit (GPU) is required.